Method for the production of slide-fastener coupling elements



March 4, 1969 H. HEIMBERGER 3,431,337

METHOD FOR THE PRODUCTION OF SLIDE-FASTENER COUPLING ELEMENTS Filed April 22, 1966 Linear Molecular/g Orienfed Synfhefic Resin Hc/muf Heimberger INVENTOR.

Attonzey United States Patent o nrsza us. or. 264-281 rm. (:1. 1529c 17/02 to tlpti Switzerland, a corporation of 3 Claims ABSTRACT OF THE DISCLOSURE Method of making continuous helicoidal coupling elements for slide fasteners wherein a synthetic-resin filament composed of linearly molecularly oriented polyamides or esters is turned about a mandrel so that each turn is buckled to form lateral protrusions constituting the coupling heads Without further shaping. The coil is then set under heat.

My present invention relates to slide fasteners and, more particularly, to an improved slide-fastener coupling element and method of making same.

It has been proposed heretofore to provide slide fasteners with tapes or other support bands along adjoining edges of which are disposed longitudinally extending coupling elements secured to the respective band. While earlier slide-fastener coupling elements were generally constituted as a chain of spaced-apart coupling bodies adapted to receiving between them the complementary coupling bodies of the other slide fastener, it has been proposed more recently to form the coupling elements of a slide fastener continuously from synthetic-resin fibers, filaments and other elongated members. In this connection, there have been many problems as to the precise configuration and structure of such coupling elements which have varied from generally planar undulating arrangements or chains to helicoidal coils whose turns are interleaved or interfitted upon closure of the slide fastener. Coupling elements of the latter type have found widespread use of late as fasteners in garments and the like which are to be subjected to rigorous washing and cleaning action (since the coupling elements are continuous and are firmly held on the tapes) and where snagging of yarn, threads, fibers and film-like materials has hitherto been a problem. The present invention is directed to such continuous coupling elements, i.e. coupling elements which extend without interruption for a major part of the length of the slide fastener.

The manufacture of helicoidal slide-fastener coupling elements from monofilamentary and preferably thermoplastic synthetic-resin wires or threads has hitherto been carried out principally by winding the elongated member upon a mandrel of suitable cross sectional configuration and thereafter setting the configuration of the strand of thermoplastic material in its coiled condition by subjecting the coil upon the mandrel to an elevated temperature at which the coil loses resiliency and, upon cooling, retains its newly imparted shape. This temperature is generally the softening point of the particular thermoplastic material, although higher temperatures, albeit below that at which the synthetic resin becomes fluid, may be employed. When reference is made hereinafter to a setting temperature or a temperature suificient to fix or set the fiber it will be understood that the intention is to indicate a temperature sufficient to overcome the resiliency of a deformed fiber and, upon cooling, permit the thermoplastic fiber to retain its configuration.

Helicoidal coupling elements may be of circular or flattened configuration and, consequently, can have a symmetrical or asymmetrical cross section or configuration. Furthermore, it has been found to be advantageous heretofore to provide the interleaved portions of the coupling elements, i.e. the interfitted parts of the mating turns of the spirals or helices, with mutually engaging heads or other formations designed to prevent mutual lateral shifting of the coils, to improve the grip with which they are held, and to lock the turns in place in a closed condition of the slide fastener. For the most part, such heads are formed by embossing the coil, under heat and pressure, with an embossing roller, press or like device, while the coil is supported by the mandrel. The pressure applied against the coil and mandrel by this method is highly disadvantageous in that considerable lateral stress is applied to the mandrel during the coil-forming operations and the mandrels often break, bend or suffer dislocations. Furthermore, the embossing rollers or heads are of varied configuration and may mar the coiling surface of the mandrel as they are urged thereagainst. Efforts to avoid possible damage to the mandrel and coiling assembly have included the step of deforming the synthetic-resin strand at spaced-apart locations by pinching devices, embossing rolls and the like. These systems were incapable of providing a satisfactory solution to the problem since the strands, subsequent to such embossment, were coiled on the mandrel but could not always be positioned accurately thereon such that the formations or heads of the strand were aligned as required. When these latter techniques were employed, moreover, extreme care was required to obtain even an approximate alignment of the heads or formations and complex control mechanisms and feed devices had to be used. In either prior arrangement, ditficulties were encountered with respect to spacing of the heads from one another and the configuration thereof.

It is, accordingly, the principal object of the present invention to provide an improved slide-fastener coupling element and method of making same.

Another object of this invention is to describe a simplified apparatus for producing an improved coupling element for slide fasteners and the like.

Yet a further object of this invention is to provide a method for the formation of continuous coupling elements with spaced-apart coupling formations adapted to be interfitted with coupling formations of an adjoining and parallel element, wherein the formations have a substantial uniform spacing and the coupling elements can be manufactured more simply, at lower cost, with greater accuracy and with reduced capital expenditure than has been possible heretofore.

The foregoing objects and others which will become apparent hereinafter are attained, in accordance with the present invention, by a method based upon my discovery that the heads or coupling formations of coupling elements for slide fasteners can be produced in situ upon the mandrel and in alignment with one another without the need for embossing devices bearing against the mandrel, when the mandrel is formed with a longitudinally extending edge about which the linear filament or thermoplastic wire can be bent and buckled or kinked so as permanently to widen the filament transversely of its major dimension and along the axis of the mandrel. Thereafter, the coil of the filament about this mandrel can be set with the aid of thermal methods known in the art. The present inven tion is applicable to the formation of generally helicoidal slide-fastener coupling elements composed of thermoplastic synthetic resins and especially the linear molecu larly oriented synthetic resin filaments composed of polyamides (nylons), polyesters and the like. The present improvement is based upon my realization that the buckling of the filament of a linear molecularly oriented synthetic resin back upon itself or about an edge or the like 3 with a radius of curvature not substantially greater than the diameter of the filament results in a substantially permanent buckling of the filament which is characterized by an enlargement of the filament transversely of the plane of the bend and, generally, symmetrical about a plane through the bend and containing the limbs of the filament adjoining the bend. The angular (as opposed to arcuate) bending of the filamentary member in this manner forms a head thereon which can serve as the coupling head or formation in place of that hitherto provided by embossing means and the like and, when the mandrel has a bending edge of a sufficiently small included angle and radius of curvature, will always be located along this bending edge. As a practical matter, it has been found that the transverse enlargement formed by the kinking or angular-bending operation described above will usually amount to 10% or more of the diameter of the filament but can attain values of 50% or more when the synthetic-resin filament is composed of a linear molecularly oriented resin (e.g. the polyamides and polyesters described above and commonly used for the formation of such coupling elements).

According to a more specific feature of this invention, an apparatus for the production of generally helicoidal coupling elements for slide fasteners or the like comprises a mandrel which is generally flattened and is provided with a relatively sharp bending edge. Advantageously, this mandrel may be of elliptical cross section or may have the configuration or a distorted ellipse (e.g., a teardrop cross section). Alternatively, the generally flattened configuration of the mandrel may involve the use of a generally fiat blade-like body of, for example, rectangular cross section.

While the coupling formations or heads produced in this manner have been found to be of a well-defined and relatively uniform nature, comparing favorably with embossed heads and the like, the embossing means hitherto required is not necessary. The kinking or buckling action is generally effected by bending the filament through a radius of curvature beyond the elastic limit so that the enlarged head remains even without thermal setting of the coil. For the most part, such a bend is effected when the limbs of the bend lie generally along an acute angle such that the radius of curvature at the bend is equal to or less than the diameter of the filament or wire. The term filament as used herein is intended to refer to any single-strand synthetic-resin elongated element of the wire, thread or like type and will be understood to include the elongated members hitherto coilable into slide-fastener elements to be attached to a tape or support band. Surprisingly, the kinking step has been found to produce a coupling formation or head which is interfittable readily with the heads of the opposing coupling element and engages the heads with which it interfits to yield a tight closure of the fastener. The kinking does not, however, disadvantageously weaken the coupling elements themselves and, indeed, coupling elements produced in this fashion have been found to have greater strength at the coupling formations or heads than has characterized heads embossed under pressure upon a coiled coupling element. 1 have found, moreover, that the configuration of the heads can be improved slightly with respect to the tightness with which they interfit with one another when a roller or the like is applied to the coils in their longitudinal direction for further deforming them in the presence of elevated temperatures (e.g., at the softening point) and pressures.

The present system has been found to be highly disadvantageous not only in that it obviates the need for embossing devices and the like and thereby eliminates the nonuniform stresses applied to the mandrel and the considerable expense of specially machined embossing rollers, but also in that it can be carried out with the aid of conventional coiling machines adapted to form coupling elements for slide fasteners. Furthermore, the improvement of the strength of the coils at the coupling heads and the greater strength with which the coupling heads interengage are most significant. Moreover, the coiling technique permits the coil to be provided with a core or aligned notches for receiving threads for connecting the coil to a support band or tape and even allows a plurality of coils to be developed simultaneously upon a movable mandrel.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is an elevational view of a filament of a linear molecularly oriented polyamide or other synthetic resin adapted to be used for the production of a slide-fastener coupling element in accordance with the present invention;

FIG. 2 is an elevational view of the coupling formation or head formed upon the filament and illustrating the operation of the present invention in diagrammatic terms;

FIG. 3 is a cross sectional view taken along the line I1IIII of FIG. 2;

FIG. 4 is an elevational view showing a pair of coupling elements in accordance with the present invention in their interconnected state;

BIG. 5 is a diagram of an apparatus embodying the principles of the present invention; and

FIG. 6 is a view taken along the line VIVI of FIG. 5.

In FIG. 1 of the drawing, there is shown an elongated filamentary body 1; of a linear molecularly oriented synthetic resin, preferably a nylon-type polyamide or polyester which is to be formed into a coupling element for slide fasteners and the like, the coupling element being mountable upon a tape or band and being provided with stop members as described in my copending application Ser. No. 534,356, filed Mar. 15, 1966, and the commonly assigned copending applications Ser. Nos. 473,002, 473,003 and 472,953, all filed July 19, 1965 (now US. Patents No. 3,353,233, No. 3,340,554 and No. 3,353,256, respectively). The present invention is directed to an improved coupling element for such slide fasteners and is based upon the principle illustrated diagrammatically in FIG. 2. When the filament 1 is bent about a sharp edge or a rounded edge so as to become kinked by a bending with a radius of curvature R (about the center of the bend C) which is smaller than the diameter D of the filament 1, the bend 3 buckles and forms a head 4 which constitutes a coupling element. As can be seen from FIG. 3, the head 4 consists of a pair of lateral protuberances 4 and 4 which extend beyond the planes P and P" of the bend 3 by amounts ranging from 10 to 50% of the diameter D of the filament 1 or greater. As has been stated earlier, these bends are effected with forces beyond the elastic limit of the synthetic resin so that the filament buckles at each bend in a lateral direction. The head formation retains its configuration even after the bending or buckling stress is removed as a consequence of the plastic deformation and may be permanently set by application of the elevated temperatures of the type used in the setting of coupling element coils and the like. As can be seen in FIG. 4, a pair of coupling elements 2 and 2 can be formed by bending the filament 1 about respective mandrels represented by a dot-dash line M for the coupling element 2, the mandrel M having a buckling edge :E about which the turns of the coil are bent sufiiciently sharply to form the heads 4' and 4" respectively. The heads are interengageable as can be seen from FIG. 4 and serve as coupling formations, the limbs extending from each head 4' or 4" lying generally in a plane P perpendicular to the mandrel M and to the major tension of the coupling elements. The coupling elements 2' and 2" can be mounted on support bands and tapes by conventional methods to form slide fasteners as described and claimed in the aforementioned copending applications.

In FIGS. 5 and 6, there is diagrammatically shown an apparatus for practicing the present invention. In FIG. 5, for example, it can be seen that the device comprises a mandrel 10 whose buckling edge 11 is adapted to sharply bend the limbs of each turn to form heads 12 upon a filament 13 fed to the mandrel via a feed means represented diagrammatically as rollers 14. The mandrel 10 is rotatable about its axis (arrow 15) and can be advanced axially (arrow 16) via a drive means 17 which determines the pitch of the turns of the helix 18 formed by the coiling device. It will be understood that the drive means 17, the feed means 14 and the mandrel 10 represent any conventional coil-winding device for the production of spiral or helicoidal slide fastener coupling elements. The mandrel is, in the present case, not a cylindrical rod but a flattened body so as to have a rectangular, elliptical or other flattened configuration with a buckling edge 11. As can also be seen from FIG. 5, the buckling operation may be facilitated by a pair of compression rollers 19, 20, adapted to be rolled longitudinally along the mandrel 10 to compress the turns thereagainst upon conclusion of a winding operation by axial movement of the mandrel (arrow 16 or arrow 21) or by corresponding movement of the rollers 19 and 20 therealong. After the buckling step has formed the heads 12 upon the turns 18 in alignment along the buckling edge 11, the mandrel carries the coil past a heating means represented at heating elements 22 and 23 in which the linear molecularly oriented and deformed thermoplastic filament is thermally set. A further roller 24 can be swept longitudinally along edge 11 to further flatten the heads 12 under heat and pressure. Upon conclusion of the treatment, the turns at 18 of the coil are led from the mandrel. In FIG. 6, it can be seen that the mandrel 10 can be of asymmetrical but ellipsoidal configuration with a bending edge 11 which can be of knife-edge or sharpened character or may merely be of extremely small radius of curvature.

It will be understood that roller arrangements may also be provided in accordance with this invention to form channels for receiving the threads designed to hold the coils to the respective tapes, with roller devices designed to provide needle openings for stitching the coils to the tapes, and die or shaping means for imparting other configurations to the coupling heads. These and other modifications will be readily apparent to those skilled in the art.

I claim:

1. A method of making continuous coupling elements for slide fasteners comprising the steps of:

helicoidally coiling a thermoplastic synthetic resin filament composed of a linearly molecularly oriented polymer;

forming coupling heads on each turn of the coil solely by buckling the filament at corresponding locations of each turn to deform the buckled portions of the filament laterally outwardly as lateral protrusions constituting part of the respective coupling head without further deformation of said filament to shape said heads, each turn of the coil being buckled by bending limbs of each turn at an acute angle about a relatively thin bending edge adapted to impart to each turn at the respective location a kinked bend of a radius of curvature less than the diameter of the filament; and

thermally setting the turns to permanently retain said coupling heads therein.

2. The method defined in claim 1 wherein said filament is coiled about a generally flattened mandrel having said bending edge to form the kinked bend at each turn of the filament about the mandrel, said synthetic resin being selected from the group which consists of molecularly oriented polyamides and polyesters.

3. The method defined in claim 2 wherein the protrusions of the filament extending laterally outwardly therefrom at the buckled portions project beyond the filament by an amount equal to 10 to of the diameter of the filament.

References Cited UNITED STATES PATENTS 3,038,207 6/1962 Schwartz 18-48 3,133,315 5/ 1964 Galonska 18-19 3,145,523 8/1964 Burbank 57-1 3,152,433 9/1964 Burbank 57-18 3,342,026 9/1967 Nichols 57-34 FOREIGN PATENTS 1,121,311 1/1962 Germany.

ROBERT F. WHITE, Primary Examiner.

RICHARD R. KUCIA, Assistant Examiner.

US. Cl. X.R. 

